1. Field Of The Invention
The present invention relates to speed limited lowering devices for removing fragile weights from significant heights. More particularly, the present invention relates to cable and harness fire escape devices for the emergency evacuation of persons from high buildings and structures.
2. Description Of The Prior Art
The architectural and construction advent of high buildings of 15 or more stories has created the need for emergency escape systems other than exterior stairways. Even the longest of powered extension ladders extend to only about 100 feet. The height of a 15 story building is in the order of 175 feet.
Controlled descent line systems have been proposed in the past but not widely adopted. Reasons for such rejection primarily relate to characteristics unique to the specific descent control system proposed but generally fall in two categories. Some prior art systems require that the descent be controlled by the user with some physical manipulation. This, of course, requires that the user be alert and physically capable: circumstances not appropriate to the very young, the elderly or unconscious victims of smoke and gas inhalation.
Other prior art controlled descent line systems are provided with a stored line reel having means to limit the reel rotational speed as line is drawn off by the user's weight. In these systems, the user rides passively in a harness secured to the lower end of the line. Although most attractive from the perspective of eliminating the need for user consciousness, strength or agility, most such prior art speed limiting reels have tended to rely on fluid energy dissipation as the reel retarding mechanism. However, like any other emergency use systems, building descent devices must be stored for long periods of time with minimal test and maintenance attention. Fluid seals deteriorate and flow restricting orifices become blocked with deposits. In other cases, polished, machine sliding surfaces seize from rust or atmospheric dust.
U.S. Pat. No. 2,976,955 to J. R. Huber discloses a hybrid type of system wherein the user hangs from a wrist sling attached to a small, centrifugal clutch retarded line speed control device driven by a threaded or helical groove sheave around which a hanging, high friction rope line is wrapped. Although a harness or other body supporting device may be substituted for the wrist sling of Huber, some tension must be maintained on the lower end of the rescue line to preclude slippage over the helical groove drive sheave. This requires consciousness and understanding by the user of the operating principle of the device. Moreover, operation of the Huber device is predicated on the high surface friction characteristics of rope, which is not only bulky for the quantities required of high buildings, but is also flammable.
Another possible inhibition to reliance on controlled descent line systems for emergency evacuation of high buildings is the lack of protection the user has from falling debris. When such buildings burn, large sheets of glass are pushed out of their mountings, sometimes intact, by the hot gas pressures generated inside the building. Additionally, heat escaping from window openings burns away the mortar securing stone sills and parapets. Victims of hotel fires throw out possessions and luggage. All of this falling debris descends to the ground in the same approximate zone as the user of a controlled descent line system. If not protected from such debris during his descent interim, the user has a high probability of receiving serious or even fatal injuries therefrom.
It is, therefore, an object of the present invention to teach the design of an emergency, controlled descent line system having no critically machined working surfaces
Another object of the invention is to teach a descent line reel speed control mechanism having no fluid to leak, seals to fail or orifices to plug.
Another object of the invention is to teach a cascaded sliding friction system for regulating the rotational payout rate of a line storage reel.
Another object of the invention is to teach a mechanical feedback system for regulating the payout rate of a line storage reel.
Another object of the invention is to teach a two-stage speed control system which permits a relatively rapid descent rate until reaching a distance of approximately 10 feet above the ground whereupon the system automatically, with no action by the user, shifts to a slower descent speed for ground approach.
Another object of the invention is to teach an automatically deployable canopy device for protecting an emergency descent line user from falling debris.